Simulacrum insta kill - bug?

I tried several times to play simulacrum and each time died at round 12 to something that I cannot explain. I play Stormveawer sorc and have 5.4K Mana, play CI and MoM (ES converted to mana) and what happens is that both bosses spawn at the same time and I die, but my mana is not spent... I had like quarter of mana left.

Since Chaos cannot pass ES, and because of MoM all damage must go through mana first, I cannot get what kills me.

Only thing that does that kind of thing is when I had mana potion that spends part of life to recover mana. Since I have 1 life and 0 sheild, it insta kills this character (didn't look at the potion while I did respec).

Is something like that in Simulacrum that I'm missing or?

And another thing, I had omen that reduces the EXP loss on death and that one didn't trigger also.

Any simmilar experience?

Happened to me once. Wasn't in simulacrum tought, it was in a delirious map. But yea, had almost full mana but got hit by something that bypassed it.

To clarify I'm not using mana potion at all and the one I have doesn't deal damage.

I'm full CI/MoM/Eb. 6k mana, wich is my whole EHP.